1. Field of the Invention
The present invention relates to flexible packages having means for selectively re-closing the packages after their initial opening. Most particularly, the present invention provides a unique re-closable flexible package that is highly consumer-friendly—especially with snack foods such as potato chips, corn chips and the like.
2. Description of the Related Art
The present invention is an improvement over existing flexible packages, including those currently used by the present assignee for containing snack foods such as Lays® potato chips, Tostitos® tortilla chips and the like. Packages for such products usually have top and bottom end seals that are formed by heat sealing and are opened by “pinch gripping” (see FIG. 1) the sides of the package and pulling outward to break the end seal for access therein. These common packages, however, do not contain means to re-close the package after the initial opening of the end seals. Because the heat seal has been destroyed, the most common way of re-closing the package is to fold-over the open end and apply a clip to secure the folded portion.
Flexible packages having re-closable zippers are known in certain applications. A variety of food products can be purchased in pre-sealed flexible packages having re-closable zippers for re-closing the food product after the initial opening.
Although a number of packages with re-closable zippers are known, the existing packages have a number of drawbacks. For example, these prior packages typically must be initially opened using two distinct steps. First, a heat seal must be broken by cutting the package with scissors or by removing a tear-away, perforated strip. The re-closable zipper closure is then opened in a distinct second step. This substantially reduces the consumer appeal of the packages and makes the packages undesirable for a variety of products, such as for snack food chips and the like.
A preferred process of packaging snack food products, such as potato chips, tortilla chips and the like, inside plastic flexible packages is known in the art as a “vertical form/fill/seal process.” In this process, as seen in FIG. 9, a length of plastic film F is formed into a vertical tube T around a product delivery cylinder C, the food product is delivered into the vertical tube through the cylinder, the vertical tube is vertically sealed along its length to form a back seal 50 and is transversely sealed to form top and bottom seals delineating individual packages, and the individual packages are cut from the vertical tube.
Providing a zipper closure to a package in a vertical form/fill/seal apparatus presents a number of difficulties. Typically, in non-vertical form/fill/seal apparatuses, a zipper is attached to an elongated moving plastic film lengthwise to the direction of travel of the film. To attach a zipper to a package in a vertical form/fill/seal apparatus, however, the zipper must be attached to the film transverse to the travel direction of the film, in order to create a package with a zipper sealed near the top end of the package.
U.S. Pat. No. 4,909,017 (assigned to Minigrip, Inc.), the entire disclosure of which is incorporated herein by reference, shows a vertical form fill process which fills product into a reclosable package having a zipper or fastener portion 34 and a pilfer-evident seal 35 above the fastener. In summary, a film is fed over shaping shoulders 21 and around a vertical forming and filling tube 24. Welding bars 22 and 23 seal edges of the film together to form a tube with a vertical seam. Welding bars 27 and 28 form a lower seal 29, and product is dropped into the vertical tube 24. The fastener strips slide over the tube 24 with only one part fixed to one side of the film tube. The fastener strips are later sealed to both sides of the film by the bars 27 and 28.
As noted on col. 4, lines 29-31, “[the] seam [35] is a pilfer-evident closure for the package and the seam can be removed cut off [sic] the tip of the package before the package is to be used.” Thus, the packages require a distinct two-step opening process.
U.S. Pat. No. 4,617,683, (assigned to Minigrip, Inc.), shows another vertical form fill process which fills product into a reclosable package having a top seal 42 and a reclosable zipper or fastener 27 inside of the package. As noted on col. 6, lines 30, et seq.,                [i]n the finished fully sealed package[,] the profiles 52 may remain separated as shown in FIG. 2 until the top end or mouth of the package has been opened as shown in FIG. 3 for access to contents in the package, and then the package can be closed by interengagement of the fastener profiles as shown in FIG. 3. Opening of the package may be effected either by pulling the seal at the top end of the package open, or by severing the too end of the package along a line 58 between the seal 42 and the reclosable fastener 27 . . . .(emphasis added). Among other disadvantages of the '683 patent, when the top end of the package must be severed to be opened, as noted above, this greatly inhibits consumer-friendliness of the packages. Another disadvantage of the '683 patent is that the initial separation of the profiles 52 (see FIG. 2) creates difficulties in the proper placement and alignment of the fastener halves on the film (e.g., in attaching fastener halves they must align at appropriate positions with respect to one another to ensure engagement). Connecting the fastener halves after the formation of the packages can thus lead to substantial alignment problems. It is notable that the '683 patent thus includes a plurality of parallel fastener profiles. (see col. 6, lines 25-29: “By having a plurality of the parallel fastener profiles 52, interengagement of the profiles of the folded section is facilitated since critical lateral alignment is not necessary.”) Another disadvantage of the '683 patent is that during manufacture, the fastener halves must be conveyed individually along with the film (e.g., must each be attached thereto); however, if the fastener halves are interlocked, one half can be attached and the other half can be carried thereon. Another disadvantage is that the fastener is exposed to the product during transport such that product can become lodged in the fastener and interfere with the operation thereof (e.g., if the package is inverted or for some reason held topside down during shipping, crumbs, etc., can accumulate within the valleys of the fastener portions).        
Other known methods, apparatuses and packages illustrative of the background art of the present invention are seen for example in U.S. Pat. Nos. 5,558,613 (assigned to Minigrip, Inc.); 5,557,907 and 5,592,802 (assigned to Illinois Tool Works, Inc.); 4,925,316 (assigned to Minigrip, Inc.); 4,709,398 (assigned to Minigrip, Inc.); 4,691,372 (assigned to Minigrip, Inc.); 5,330,269 (assigned to Toyo Aluminum Kabushiki Kaisha); 5,067,822 (assigned to Reynolds Consumer Products, Inc.); 4,782,951 (assigned to Oscar Mayer Foods Corp.); and 4,976,811 (assigned to Com-Pac International, Inc.